While Russian officials have categorically denied the government's involvement in the hacks, NBC reports that Putin himself was behind the scenes directing efforts to undermine the U.S. election.

His motivation began as a "vendetta" against Democrat Hillary Clinton, according to NBC, but turned into an effort to raise concerns about corruption in U.S. politics and to "split off key American allies by creating the image that [other countries] couldn't depend on the U.S. to be a credible global leader anymore," the official told NBC.

Intelligence officials now have a "high level of confidence" that Putin was personally involved, though they did not elaborate on the evidence.

"It is most certainly consistent with the Putin that I have watched and used to work with when I was an ambassador and in the government," former U.S. ambassador to Russia Michael McFaul told NBC.

"He has had a vendetta against Hillary Clinton, that has been known for a long time because of what she said about his elections back in the parliamentary elections of 2011. He wants to discredit American democracy and make us weaker in terms of leading the liberal democratic order. And most certainly he likes President-elect Trump's views on Russia."